Abstract Background There is insufficient validation of diagnostic benefits of extended monitoring with an adhesive single-lead ECG device compared to Holter test for routine medical care of AF patients. Purpose The study aimed to compare AF detection rates between 72-hour monitoring using an adhesive single-lead ECG device (mobiCARE MC-100, Seers Technology, Republic of Korea) and 24-hour Holter test among AF patients at outpatient clinics. Methods A total of 200 AF patients indicated for Holter test at cardiology outpatient clinics enrolled in the study. Study participants equipped both Holter and MC-100 for the first 24 hours (Figure 1). After then, only MC-100 continued ECG monitoring for additional 48 hours. AF detection during the first 24 hours was compared between two devices. The diagnostic benefits of extended monitoring with MC-100 were evaluated. Results During the first 24 hours, both monitoring methods detected AF in the same 40/200 (20.0%) patients (20 patients with paroxysmal and persistent AF each). Compared to 24-hour Holter, MC-100 increased AF detection rate by 1.5-fold (58/200; 29.0%) and 1.6-fold (64/200; 32.0%) with 48- and 72-hour monitoring, respectively (Figure 2A). With MC-100, the number of newly discovered patients with paroxysmal AF was 20/44 (45.5%), 18/44 (40.9%), and 6/44 (13.6%) for 24-, 48-, and 72-hour monitoring. Compared to 24-hour Holter, 72-hour monitoring with MC-100 increased the detection rate of paroxysmal AF by 2.2-fold (44/20). If only the episodes lasting over 30 seconds were counted as AF with MC-100, the detection rate of paroxysmal AF was decreased by 9.1% (Figure 2B). Conclusion Compared to Holter, AF detection rates could be improved with an adhesive single-lead device, especially for patients with paroxysmal AF. This device is expected to be useful for AF detection among patients whose conventional ECG tests were ineffective in documenting AF episodes. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Korea Medical Device Development Fund grant funded by the Korean government (the Ministry of Science and ICT, the Ministry of Trade, Industry and Energy, the Ministry of Health & Welfare, Republic of Korea, the Ministry of Food and Drug Safety)